The seasons are due to the change of the Earth’s position in
the course of its revolution about the Sun, and to the inclination of its axis.
The Equator is an imaginary line drawn round the Earth midway between the
Poles. There are two other lines, namely, Tropic of Cancer (23½O N) and the Tropic of Capricon (23½O S). The word tropic means, ‘turning
place’. The inclination of the Earth’s axis together with its revolution round
the Sun is the cause of the varying length of day and night in different parts
of the world. On March 21 (Vernal Equinox) and September 23 (Autumnal Equinox)
the Sun is overhead at the Equator. On these dates, except at the Poles, (a)
days and nights are equal all over the world; and (b) the Sun rises exactly due
east and set exactly due west at all places on the Earth’s surface. At the
Equator itself days and nights are equal throughout the year. Between March 21
and September 23, when the North Pole is tilted towards the Sun, the days are
longer than the nights throughout the Northern Hemisphere and there is continuous
daylight at the North Pole. Similar conditions are experienced in the Southern
Hemisphere and the South Pole between September 25 and March 21.

Latitude
and Longitude:

Latitude
is distance, measured in degrees, north or south of the Equator. Longitude is
distance, measured in degrees, east or west of any fixed meridian. The meridian
passing through Greenwich is numbered 0O. On a globe the meridians are numbered from 0O to 180O
E (East) or W (West). At the equator
the degrees are 69 to 70 miles apart (25000÷360). Since earth completes one
rotation on its axis in 24 hours, 360 meridians pass under the Sun in

that
time. Therefore, 1 degree passes under the Sun every 4 minutes.

International
Date Line:

If
we travelled westward to a place X on longitude 180o W, the time there would be 12 hours
behind Greenwich time (180 x 4 minutes = 720 minutes = 12 hours). If we
journeyed eastward to a place Y on longitude 180o E, the time there would be 12 hours ahead of Greenwich time.
Thus X and Y both on 180o have
the same time but

The
Earth and the Solar System :

The
Earth is a member of the Solar System. It is one of nine major planets revolving
round the Sun. Of these, Mercury and Venus are nearer, and Mars, Jupiter,
Saturn, Uranus, Neptune and Pluto are farther away from the Sun than the Earth.
The planets radiate no light of their own, but shine with that reflected from the
Sun. The Sun has a diameter of 864,000 miles (1,390,000 Kms) and it is
93,000,000 miles (150,000,000 Kms) from the Earth. The Sun is a star. The stars,
unlike the planets, are self-luminous bodies. The other stars appear small
because they are so far away; the nearest star, Proxima Centauri, is 200,000
times more distant from us than the Sun. The Moon is a dead planet. It is about
240,000 miles (386,000 Kms) from the Earth. The Moon revolves round the Earth
taking approximately 29 days to complete one round. The phases of the Moon are
the result of its position in relation to the Earth and the Sun. The Moon’s
orbit is ecliptical and inclined at an angle of 5o
to the plane of the Earth’s orbit. This
explains why we do not have a total eclipse of the Sun every time there is a
new moon.

The
Earth:

The
Earth is a sphere but it is not a perfect sphere. It is slightly flattened at
the poles and bulges at the equator. The circumference of the earth is
approximately 25,000 miles (40,000 Kms). It rotates on its axis once in every
24 hours, spinning from west to east. Besides spinning on its axis, it also moves
round the Sun, called the revolution. Its orbit round the Sun is
oval or ecliptical. The time taken to complete one revolution is approximately
365¼ days or one year. For convenience, one year is taken as 365 days and the
shortfall of ¼ day each year is made good in the Leap Year which consists of 366
days. The Earth’s axis inclined to the plane of its orbit at an angle of 66½O.differ in date by a day (12 hours + 12 hours = 24 hours). To overcome the confusion that would otherwise arise,the International Date Line has been established. It runs along 180o E or W. Westward-bound vessels crossing the Date Line drop a day from the calendar, while those going eastward add a day by giving the same date to two consecutive days. Instead of changing the time exactly according to change in degrees at the rate of 4 minutes per degree, certain time zones have been established. All places in the same area or time zone or time belt, use what is called Standard Time. Thus we have the Greenwich Mean Time (G.M.T) and the Indian Standard Time (I.S.T). There are five time-belts in Canada and four

The
Lithosphere:

The
mass of the Earth is generally divided into three layers, namely, Crust, Mantle
and Core. The Lithosphere is the name given to the outer Crust which is
not more than 10 miles thick. It is made up of a great variety of rocks, soils,
etc.

Rocks:

1.
Sedimentary Rocks:These rocks are made up of deposits laid down on the
floor of river beds, lakes

and
seas. Examples:Sand and sandstone, clay, lime stone, chalk and
carbonaceous rocks, such as lignite, coal

and
anthracite.

2.
Igneous Rocks:These are primary rocks which are formed by cooling and
solidification of molten lava. When such rocks are poured out on the surface they
are known as Volcanic rocks, e.g. basalt. When the molten material solidifies
at considerable depth, plutonic rocks are formed, e.g. granite.

3.
Metamorphic Rocks:These rocks are formed as a result of alteration by
extreme heat and or pressure of igneous or sedimentary rocks. Example,
slate, gneiss, schist etc.

Soil:

The
upper layers of rocks weather to form the soil. There are three distinct layers
of soil. The uppermost layer forms the top soil. The second layer is called the
subsoil. The third layer is made up of decomposing and much-broken rock, known
as mantle- rock. The type of soil depends on a number of factors, namely,
climatic conditions, the nature of the parent rock, relief, vegetation and the
period over which it has been worked by man. Soils may by broadly classified as
(a) Forest, (b) Grassland and (c) Desert types.

Mountains:

In
past geological ages disturbances in the Earth’s interior have caused crumpling
and cracking of the crust. This has resulted in great upholds forming Fold-Mountains
which are mainly made up of folded strata of sedimentary rocks, e.g. the
Alps, the Rockies, the Andes, and the Himalayas. The mountain structures worn
down by prolonged denudation are known as Residual Mountains, e.g. Highlands of
Scotland and Scandinavia.

Denudation:

The
process known as denudation or the wearing away of the land is continually
going on. The chief causes of such erosion are (a) changes in temperature; (b)
frost; (c) winds; (d) water, including rivers; (e) ice; and (f) the action of
the sea. Steps to combat soil erosion include (i) terracing; (ii) contour ploughing;
(iii) strip cropping (iv) planting shelter belts of trees; and (v) plugging the
gullies by building small dams etc.

The
Atmosphere:

The
air is composed mainly of nitrogen (78%) and oxygen (21%) with small
proportions of carbon dioxide, water vapour and rarer gases like argon and
neon. Atmosphere is 200 miles thick, but nine-tenths of the air composing it is
found within 12 miles, and half within 3½ miles of the earth’s surface. We are
concerned mainly with the lower layer of troposphere. The upper layers
in the ascending order are Stratosphere, Mesosphere and Ionosphere. Troposphere
extends to a distance of about ten kilometres. Stratosphere is a
region extending from an altitude of about 11 Km to 50 Km above the earth. The upper
part of stratosphere has plenty of ozone which protects us from the fatal
effects of Sun’s ultraviolet radiation. Mesosphere is the next layer
extending from 50 to 80 Kms above the earth. It is a very cold region. Ionosphere
extends from about 60 Kms upwards. It includes Thermosphere and Exosphere
which marks the outer limits of the earth’s atmosphere.

Wind
is air in motion:

The
chief cause of wind is difference in atmosphere pressure. One of the main
reasons for differences in

pressure
is unequal heating of the air. From the high pressure belts the air flows
outwards to the regions of low pressure. Owing to the rotation of the earth,
the winds do not blow due north and south, but are deflected. In this deflection
they obey Ferrel’s Law which states, “Any moving body on the earth
surface including a current of air, tends to be deflected, the deflection being
to the right in the northern hemisphere and to the left in southern hemisphere.”
Land and seabreezed are local winds caused by the unequal heating of
land and water. During the day the land becomes very much hotter than the sea,
with the result that there is marked low pressure over the land. Thus
the air over the sea flows rapidly loses heat, but the sea remains warm for a
longer time. Thus at night, heavy cool
air blows from the land to take the place of warm air rising over the sea. The monsoon
or seasonal winds may be
regarded as land and sea breezes on a large scale, in which the time-frame is a
year instead of a day. This phenomenon
is to be found in south-east Asia, but is especially marked in the subcontinent
of India. A cyclone is
a portion of the atmosphere in which the pressure is lowest in the centre. The
winds blow inwards in anticlockwise

direction
in the Northern Hemisphere. In the Southern Hemisphere cyclonic winds blow in a clockwisedirection in accordance with Ferrel’s Law. An anticyclone is a portion of the atmosphere in which the pressure is highest in the centre. The winds blow outwards in a clockwise direction in the Northern Hemisphere and in an anti-clockwise direction in the Southern Hemisphere.The Oceans: It is estimated that 72% of the surface of the globe is covered with water. The Pacific, which is the greatest of all oceans, covers a third of the earth’s surface, its total area being greater than that of all the dry land. Atlantic is slightly less than half the size of the Pacific, yet so many great rivers flow into it that it receives half the drainage of the world. The other oceans are Indian, Mediterranean, Antarctic and Arctic. The average depth of the ocean is 12,500 feet, compared with the average height of the land which is about 2,500 feet. The greatest known depth is that of the Marianas Trench in the Pacific, where a depth of 35,800 feet has been recorded. Tides: Tides are caused by the gravitational attraction - the ‘pull’ of the moon on the earth, sometimes assisted by and sometimes hindered by the Sun.At new and full moon, when the Sun, Moon and Earth are practically in a straight line the attractive force of the Sun increases that of the Moon. Such high tides are called spring tides. Weather and Climates: Weather may be defined as the condition of the atmosphere at any place at a particular time. The average weather conditions determine the climate. Humidity, temperature, elevation, distance from the sea, ocean currents, atmosphere pressure and prevailing winds combine to affect the climate of a region. Humidity: Humidity, the term used to express the dampnessof the atmosphere, is due to the pressure of water vapour. Evaporation is the mean by which water is drawn off as invisible water vapour from oceans, lakes, rivers, etc., when the air contains as much water vapour as it can hold is said to be saturated. When saturated air is cooled, condensation takes place and some of the water which form the clouds grow larger, they precipitate i.e., fall to the earth as rain. The proportion of water vapour in the air, compared with the maximum it can hold at the same temperature, is known as Relative Humidity. Dew is caused by the condensation of water vapour on the cold ground during the night. The temperature at which such condensation takes place is called the Dew Point. Whencondensation takes place near the surface (and not on the ground) the result is usually mist or fog. Whencondensation takes place at some distance from the ground, clouds are formed. When water vapour is condensed at a temperature below freezing point it forms snow. There are various kinds of clouds. The layer like clouds often seen on the horizon at sunrise and sunset are called stratus clouds. The light wispy clouds formed high in the sky are called cirrus clouds. The heaped up clouds, looking rather like masses of cotton wool are called cumulus clouds. The black rain clouds are known as nimbus. Temperature: Of all climatic factors, temperature is the most important. It affects man’s food, crops, dress and the type of dwelling he builds. Temperature decreases 1oF for every 300 feet above the sea-level. This decrease is largely due to the fact that the rarified air, found in elevated regions, absorbs less heat than the denser air at lower levels.SEVEN NATURAL WONDERSOF THE WORLD1. Mount Everest, on the border of Tibet and Nepal.2. The Nile River, Egypt.3. Rio de Janeiro Harbour.4. Iguassu Falls, Argentina.5. Yosemite Valley and the Giant Sequioas of California.6. The Grand Canyon, Colorado River, Arizona.7. The Northern Lights, especially from NorthernCanada and Alaska.SEVEN WONDERS OF TODAY1. The Taj Mahal of Agra, India.2. The Great Pyramid of Egypt and the adjacent GreatSphinx of Gizeh.3. Hagia Sophia, 6th Century, in present day Istanbul.4. Leaning Tower of Pisa, Italy.5. The Eiffel Tower, Paris.6. The Washington Monument, Washington.7. The Empire State Building, New York City.SEVEN WONDERSOF THE ANCIENT WORLD1. The Pyramids of Khufu2. The Hanging Gardens of Babylon3. The Temple of Artem is at Ephesus4. The Statue of Zeus at Olympia5. The Mausolus at Halicarnassus6. The Colossus of Rhodes7. The Pharos (Lighthouse) at AlexandriaSEVEN WONDERSOF THE MEDIEVAL WORLD1. The Colosseum of Rome2. The Great Wall of China3. The Porcelain Tower of Nanking, Cahina4. The Mosque at St.Sophia (Constantinople)5. The Stonehenge of England6. The Catacombs of Alexandria7. The Leaning Tower of Pisa

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About Me

The name "Khit Ponnya" is Mon language that mean "knowledgeage". Khit Ponnya is a small group of producing Mon magazine to educate Mon people and to let them patriotism in Mon nation because nowadays, Mon people are having less patriotism. in this case, Mon people will disappear one day in this earth. So, to maintain Nation, Culture, tradition, language and history, we are grouped as the name of Khit Ponnya to educate them. To know about Mon People going to see this link http://en.wikipedia.org/wiki/Mon_people